JohnMo

Most if not all Viessmann products are designed to run weather compensation via their own controllers, and can run two zones at different flow temps if required via a fully open system without thermostats or trvs. So why mess with that? By putting a third party thermostat that will give less control or worse efficiency. Run as the Germans intended

Because they give a set delta T, they auto balance the system as and when actuators open and close, so a loop always has a set delta T. In this situation @Adsibob is supplying too much energy in to a loop and the way to balance this, is to increase delta T over the loop, so the mean flow temperature reduces

You don't need to do anything complex. For the rooms that overshoot 0.4 - do nothing for now. For the 1.9 overshoot you are putting too much energy in the floor. Reduce that loops flow rate by 0.5L/min. Monitor and adjust as required. Less flow less energy, more flow more energy, adjust at the loop flow meters. Auto balance actuators will not help with this. Once your room over shoots are all roughly the same, reduce flow temp a degree at a time. If you hot water and CH are set at different flow temps you can reduce the flow temp to CH at the boiler.

Not many users on the database. Not surprising when they want £600 for a monitoring kits.

Dump the zones go single zone, balance the flow rates to equalise the heat dumped in to room. Gas boilers are usually way to big and struggle on low heat demands.

How do you model the radiator DT, with a variable temperature system, as DT would continually be changing in the WC system. I know on my boiler that if I set the flow temp at 30 degrees the pump will be modulated to manage a DT of 4, if I increase the flow temp to 70 the pump flow rate is managed to give a DT of around 20. Your DT is only really fixed at a set design temperature, form then on it moves, based on flow temp and room temp, the closer the room temp gets to radiator temp the less work the radiator does so the DT changes.

Or a volumiser, in the flow or return piping, then there is no mixing of the flow and return water. Or if installing a buffer install as a 2 port buffer between the flow and return, so its only engaged as zones close off. Or stop zoning everything in to small areas/water volumes. A recent test (simulation) was showing a reduction of 1 on CoP, with buffer compared to without buffer. Both running WC, but with buffer HP required increased HP flow temps to overcome the mixing within the buffer. If your are getting a couple of batches of cheap electric, a large buffer could be beneficial even with the hit in CoP. But you would need a low energy consumption house to make a real benefit or a very large buffer.

But then your CoP takes a hit

That's a good piece of work Think UFH curve is just 1 for 1 instead of 1.3 Just plotted outside temp from -10 to 20 in one column and the formula next column Added my WC curve to your spreadsheet and due to lower flow temps of UFH ended up with a projected CoP of 4.82 on WC, but the savings against a fix flow temp were low only 5%. CoP changes to 4.59.

that subject to not being so large it ends up cycling to much. we are on 300mm centres and loop lengths matched to the heat loss of the room. 16mm tube max length used is 100m. To date we have not had to flow any warmer than 34 degs even at -9 outside temp. We have Ivar manifold and mixer. Did have actuators, then Salus self balancing, now they have all be removed and run a open system on a single zone. Soon to install a 6kW pump, heating house and summer house. The thing with UFH is your house doesn't need to be hot to feel comfortable. Our is rarely above 19 deg unless the wood stove is on or we get solar gain. Glycol would only be needed for a heat pump, or anti freeze valves in leu of glycol

Good idea So just form standalone walls within walls, should be easy enough to do and zero strain on anything

So been reading up. A log building like this can grow and shrink quite a bit. Any battens directly screwed to the logs can place a restriction on this action and lead to splits and cracks. The normal way it seems to attach at batten is to use an angle bracket, this attached to the batten with two screws and to log with a single screw in a slot within the bracket, this allows the building to grow or shrink without effecting the internal wall. The internal wall stops about 50mm short of full height and skirt is formed from the ceiling to cover the gap, as a sliding panel. So my thoughts are a variation on @Iceverge suggestion. Wrap the internal walls in a breather membrane. Then attach 100mm battens at 600mm centres via sliding brackets to the logs. Stop 50mm short of full height. Full fill with rockwool or similar up to roof. VCL fully taped on walls and ceiling. Roof external 100mm PIR. How does that sound?

Interested - So what inputs did you use to get your data points?

That's huge, you will need an intercom system to speak to anyone. We have 3 large bedrooms and 3 bathrooms in the same space. I assume your loo will become the accessibility toilet sink ect, but sounds to small at 3m2. Seems at lot of house for just 2 bedrooms?

Are your calculations allowing for glycol or no glycol in the water mix. This could 10-15% of energy meter reading.

Why would you use a liquid DPM for a new build. Your DPM isn't for airtightness it's to stop ground water transfer in to the building structure.

To many variables to comment on, the house may be huge, the heat pump huge, setting everything at high temps, loads of zones, heat pump cycling, poorly commissioned. Do the same with gshp you would get a similar outcome. PV in winter output is the just about zero anyway, so will have little or bearing on monthly heating bills. Many on here get excellent cost effective heating from an ASHP. Mostly down to how you set things up and operate, keeping flow temps as low as practical.

So what flow temp is the ASHP using to achieve a cylinder temp of 51 in 45 mins. Assume must have a big heating coil. Flow temp 65, CoP close to 1.2 60, CoP close to 2.5 55 cop CoP close to 3 All the above are on a 5 deg day. Depending how many times you heat the cylinder in a day, could have a marked influence on your electric consumption.

Only thing I would say about 35mm battens, with plumbing is there may not be enough room for pipe clips.

They just use the nearest weather station to your post code, and use a historical average. For us they would use Dyce airport (60 miles away), which can on average be 3 deg colder than where we live due to a micro climate. But obviously close enough. They are only looking for magnitudes of heat loss. Do they use a 3, 6, 9, 12... kW heat pump.

Let's simplify a little. You are using more electric than you expected your CoP looks rubbish, except on one day where you got around 3.5 instead of 4.5. I think that sums it up. Issues, you have a buffer, loose 1 from your CoP. Way to many zones, merge most of them together ideally have one or two large zones. DHW, this can be a huge consumer, assuming from ASHP. So how is it heated? Cylinder set temp? Flow temp to cylinder? Does the ASHP see cylinder water temp or is it on/off signal from thermostat? Do you have an immersion hooked up to ASHP controller?

Pump speed is just a tool to get your required flow rate. Speed is adjusted to over the system resistance, if you have the flow rates you want and speed is to high you are just wasting electric. Nothing to do heat transfer, except providing the motive force to move the water at your set flow rate Temp, on its own isn't the whole story, it's the combined outcome of flow temp and return temp, so the mean flow temp that sets the kW output. Flow rate alters the mean flow temp. You also have floor covering u value to add to the mix. The more resistant the higher the mean temp needs to be for a give kW output.

Doesn't u value required tie in directly to the form factor. Two storey nearly a cube would need way less insulation than my house, long thin, and single storey with all sloping ceiling. My house to comply with PH heat loss would require u values all below 0.1.

Having a buffer will knock about 1 of your expected CoP. But doesn't account for all your excess electrical consumption. Sorry for lots of questions. How long is your heat pump running for is at least 10 mins Are all the zones on at once, or at different times.

So how is your buffer plumbed, is the normal 4 port, any idea of the size. Is it controlled by a thermostat?